A few days after the events of September 11, this newspaper published a response by Jay McInerney, supposedly the creator of "the definitive modern New York novel". He told us that on that very Tuesday, still shaken and shocked, he took lunch at Time Café, "a once fashionable dining spot". And who should immediately enter but "the actress Jennifer Beals... a camera around her neck, looking slightly dazed".

Later, McInerney repairs to the apartment of another New York novelist, Bret Easton Ellis. On Bret's kitchen counter he sees an invitation to a literary party, and blurts out: "I'm glad I don't have a book coming out this month" - a statement he knows to be "a selfish and trivial response to the disaster, but one I thought he would understand." Bret replies that he was just thinking the same thing. Then Jay says to Bret: "I don't know how I'm going to be able to go back to this novel I'm writing." He adds, to the reader: "The novel is set in New York, of course. The very New York which has just been altered for ever."

Is McInerney right? Will the horrid alteration of America's greatest city also alter the American novel? One is naturally suspicious of all the eschatological talk about how the time for trivia has ended, and how only seriousness is now on people's minds - not least because the people saying it are usually themselves trivial and, as in McInerney's piece, are thus unwitting arguments against their own new-found seriousness. Doubtless, trivia and mediocrity will find their own level again, in novel-writing as in everything else. And besides, the "New York novel" - as opposed to the novel set in New York - is a genre of no importance at all. If I live the rest of my life without having to come across another book like Bret Easton Ellis's New York novel, Glamorama, I will have very happily been what Psalm 81 calls "delivered from the pots".

There has, of course, been great fiction set or partly set in New York: Melville's story "Bartleby", which is set in a Wall Street office; Stephen Crane's Maggie; The Great Gatsby; the last section of Theodore Dreiser's novel, Sister Carrie, which rails splendidly against the capitalist inequities of what Dreiser calls "the Walled City"; a chapter of Céline's Journey to the End of the Night; Henry Roth's great novel of immigrant life, Call It Sleep; Bellow's Seize the Day and Mr Sammler's Planet. Yet as soon as one recalls these novels, it becomes difficult to imagine the precise ways in which they would have been different had they had to accommodate a mutilation of the kind visited upon the city on September 11. And that is partly because they are already dark books, in which the city looms jaggedly. It is only the McInerneys, for whom Manhattan is a tinkle of restaurants, who are suddenly surrounded by the broken glass of their foolish optimism. The pessimist is already ruined, and knows it.

What also unites these dark works of fiction is that their foci are human and metaphysical before they are social and documentary. They are stories, above all, about individual consciousness, not about the consciousness of Manhattan. Here, terrorism may well have an impact. For after all, the dream of the Great American Novel has for many years really been the dream of the Great American Social Novel - certainly since John Dos Passos and Sinclair Lewis.

The Great American Social Novel, which strives to capture the times, to document American history, has been revivified by Don DeLillo's Underworld, a novel of epic social power. Lately, any young American writer of any ambition has been imitating DeLillo - imitating his tentacular ambition, the effort to pin down an entire writhing culture, to be a great analyst of systems, crowds, paranoia, politics; to work on the biggest level possible.

The DeLilloan idea of the novelist as a kind of Frankfurt School entertainer - a cultural theorist, fighting the culture with dialectical devilry - has been woefully influential, and will take some time to die. Nowadays anyone in possession of a laptop is thought to be a brilliance on the move, filling his or her novel with essaylets and great displays of knowledge. Indeed, "knowing about things" has become one of the qualifications of the contemporary novelist. Time and again novelists are praised for their wealth of obscure and far-flung social knowledge. (Richard Powers is the best example, but Tom Wolfe also gets an easy ride simply for "knowing things".) The reviewer, mistaking bright lights for evidence of habitation, praises the novelist who knows about, say, the sonics of volcanoes. Who also knows how to make a fish curry in Fiji! Who also knows about terrorist cults in Kilburn! And about the New Physics! And so on. The result - in America at least - is novels of immense self-consciousness with no selves in them at all, curiously arrested and very "brilliant" books that know a thousand things but do not know a single human being.

Zadie Smith is merely of her time when she says, in an interview, that it is not the writer's job "to tell us how somebody felt about something, it's to tell us how the world works". She has praised the American writers David Foster Wallace and Dave Eggers as "guys who know a great deal about the world. They understand macro-microeconomics, the way the internet works, maths, philosophy, but... they're still people who know something about the street, about family, love, sex, whatever."

But this idea - that the novelist's task is to go on to the street and figure out social reality - may well have been altered by the events of September 11, merely through the reminder that whatever the novel gets up to, the "culture" can always get up to something bigger. Ashes defeat garlands. If topicality, relevance, reportage, social comment, preachy presentism, and sidewalk-smarts - in short, the contemporary American novel in its current, triumphalist form - are novelists' chosen sport, then they will sooner or later be outrun by their own streaking material. Fiction may well be, as Stendhal wrote, a mirror carried down the middle of a road; but the Stendhalian mirror would explode with reflections were it now being walked around Manhattan.

For who would dare to be knowledgeable about politics and society now? Is it possible to imagine Don DeLillo today writing his novel Mao II - a novel that proposed the foolish notion that the terrorist now does what the novelist used to do, that is, "alter the inner life of the culture"? Surely, for a while, novelists will be leery of setting themselves up as analysts of society, while society bucks and charges so helplessly. Surely they will tread carefully over their generalisations. It is now very easy to look very dated very fast.

For example, Jonathan Franzen's distinguished new novel, The Corrections , has just appeared in America. It is a big social novel trying hard not to be one - softened DeLilloism. Franzen has announced a desire to take the DeLillo model and warmly people it with characters. It's an admirable project. But there is a passage near the end of The Corrections about the end of the American 20th century that is pure social novel, and which now seems laughably archival: "It seemed to Enid that current events in general were more muted or insipid nowadays than they'd been in her youth. She had memories of the 1930s, she'd seen firsthand what could happen to a country when the world economy took its gloves off... But disasters of this magnitude no longer seemed to befall the United States. Safety features had been put in place, like the squares of rubber that every modern playground was paved with, to soften impacts." As McInerney might say, "I'm glad I don't have a novel coming out this month."

The other casualty of recent events may well be - it is to be hoped - what I have called "hysterical realism". Hysterical realism is not exactly magical realism, but magical realism's next stop. It is characterised by a fear of silence. This kind of realism is a perpetual motion machine that appears to have been embarrassed into velocity. Stories and sub-stories sprout on every page. There is a pursuit of vitality at all costs. Recent novels by Rushdie, Pynchon, DeLillo, Foster Wallace, Zadie Smith and others have featured a great rock musician who played air guitar in his crib (Rushdie); a talking dog, a mechanical duck and a giant octagonal cheese (Pynchon); a nun obsessed with germs who may be a reincarnation of J Edgar Hoover (DeLillo); a terrorist group devoted to the liberation of Quebec who move around in wheelchairs (Foster Wallace); and a terrorist Islamic group based in North London with the silly acronym Kevin (Smith).

Rushdie was at it again in his most recent book, Fury, a lamentable novel that combined hysterical realism - dolls, puppets, allegories, a coup on a Fiji-like island, rampant and tiresome caricature, and a noisy, clumsy prose - with the more traditional social novel. Alas, the social-novel part of the book was set in Manhattan, and offered a kind of diary of last year's Manhattan events. We encountered Rudy and Hillary, J-Lo, the Puerto Rican parade, Bush versus Gore, the film Gladiator and so on. Of course, the book was already obsolete when it appeared in early September, just before the terrorist attack. Its trivia-tattoo had already faded. But now it seems grotesque, a time-stamped scrap of paper.

It ought to be harder, now, either to bounce around in the false zaniness of hysterical realism or to trudge along in the easy fidelity of social realism. Both genres look a little busted. That may allow a space for the aesthetic, for the contemplative, for novels that tell us not "how the world works" but "how somebody felt about something" - indeed, how a lot of different people felt about a lot of different things (these are commonly called novels about human beings). A space may now open, one hopes, for the kind of novel that shows us that human consciousness is the truest Stendhalian mirror, reflecting helplessly the newly dark lights of the age.